Advances in electronic technology cause integrated circuits to be formed on substrates such as silicon wafers with ever increasing packing density of active components. The formation of circuits is carried out by sequential application, processing, and selective removal of various components from the substrate. Various compositions have been developed for removal of specific classes of components from substrates in semiconductor wafer technologies. For example, a composition commonly denoted SC-1, which contains a mixture of NH4OH (29 wt %)/H2O2 (30 wt %)/water at a volume ratio of about 1:1:5 (or at somewhat higher dilution ratios), is typically used to remove particles and to reoxidize hydrophobic silicon surfaces. Similarly, a composition commonly denoted SC-2, which contains a mixture of HCl (37 wt %)/H2O2 (30 wt %)/water at a volume ratio of about 1:1:5 (or at somewhat higher dilution ratios), is typically used to remove metals. An additional composition, commonly called a Piranha composition, comprises H2SO4 (98 wt %)/H2O2 (30 wt %) at a volume ratio of about 2:1 to 20:1, and is typically used to remove organic contamination or some metal layers.
Photoresist materials are used in many circuit manufacturing processes to assist in formation of sequential layers. In stages of the manufacturing process, these photoresist materials are often removed, preferably without substantial damage to the substrate, including structures formed thereon. Photoresists are conventionally removed using organic solvents, such as n-methyl-pyrrolidone (“NMP”), glycol ether, amine, or dimethyl sulfoxide (“DMSO”). Alternatively, photoresist materials have been removed using inorganic chemical agents such as sulfuric acid and hydrogen peroxide, or using reactive gaseous chemicals generally known as photoresist plasma ashing. U.S. Pat. No. 5,785,875 discloses a method for removing photoresist material by carrying out a wet acid etch by fully submerging the wafers within anhydrous acid, and draining the etching agent from the chamber while inserting a heated solvent vapor. The solvent is, for example acetone, alcohols, or another solvent, but preferably comprises isopropyl alcohol, and is heated to the range of between about 50° C. and about 100° C. Traditional wet chemical processes used to remove photoresist rely on concentrated sulfuric acid combined with hydrogen peroxide (Piranha or “Sulfuric-Peroxide Mix” or SPM) or ozone (sulfuric-ozone mix or “SOM”). Alternatively, photoresists can be removed under certain conditions by using ozone dissolved in DI water or by mixing ozone gas with water vapor at elevated temperatures.
Particularly challenging is the removal of patterned photoresist that has been subjected to ion implantation processes, which cause hardening of the resist surface. An approach to removing this implanted photoresist is to increase the temperature of the chemical treatment. Additionally, removal of dopants that are applied to substrates by plasma doping can be very difficult. US Patent Publication No. 20070243700 describes a technique whereby the dopant-containing layer is stated to be removed from the photoresist layer by exposing the dopant-containing layer to a water rinse, a chlorinated plasma or to a fluorinated plasma.
It would be desirable to identify alternative techniques and compositions for treatment of substrates, particularly to remove materials, especially organic materials, and most especially photoresist materials from substrates such as semiconductor wafers.